This invention relates to fuel injectors for engines and, more particularly, to methods of assembling a fuel injector body designed to include a step of furnace brazing.
It is known in the art relating to engine fuel injectors that joints between injector body components that carry fuel under pressure must be hermetic to prevent fuel leakage. They must also provide sufficient mechanical strength to resist a change in performance upon assembly into an engine and under adverse operating conditions. Typical joint designs for injectors utilize seam welds or elastomeric seals with a mechanical joint to provide the required performance. However, elastomeric seals may require excessive space for use in more compact injector designs. Laser seam welds may be used but require access to the joint for the laser beam which may require additional assembly steps or special design features.
The present invention provides injector designs and assembly methods which make possible the assembly of a compact injector body using a single step of furnace brazing to seal one or more joints.
As applied to related plunger and disk valve injector designs, an assembly method for a fuel injector body having an internal hermetic and structural joint includes, providing an annular body member with an annular inner recess having an inner cylindrical surface and forming an annular end recess adjoining the cylindrical surface, fitting a tubular member into the inner recess of the body member with an outer surface of the tubular member engaging the cylindrical surface of the inner recess, placing a brazing ring in the end recess of the body member adjacent the tubular member, and furnace brazing the members together to form the internal hermetic and structural joint.
Certain disk valve injectors have a body with a magnetic outer ring and a magnetic inner tube, forming outer and inner poles connected radially by outer and inner cylindrical joints to a non-magnetic spacer ring and a cylindrical inner surface of the spacer ring effectively forms an inner recess. A specific assembly method for such injectors includes positioning an upper surface of the spacer ring below upper portions of the outer ring and the inner tube to form an end recess therebetween, placing a brazing ring in the end recess, and furnace brazing the cylindrical joints to form internal hermetic and structural joints. This method fixes and seals both inner and outer joints in a single furnace brazing operation.
The addition of an additional outer member by hermetic laser seam welding is also contemplated in the methods.